Influence of lakes on catchment hydrology and stream temperature

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Climate change, forest disturbance, and urbanization are having a profound impact on the health of streams and their aquatic ecosystems. Developing a process understanding of how these environmental changes are impacting streamflow regimes and water quality is critical for effective management of our water resources. A glaring knowledge gap in our understanding of how catchments respond to environmental change is the role of lakes on downstream hydrology and water quality. Empirical studies have highlighted the important influence of lakes on stream water quality at landscape scales, even when lakes comprise just a small fraction of the landscape area. However, only a few studies have focused on the hydrologic and thermal processes underpinning these landscape patterns. In addition, most research has focused on large lakes and their inlet and outlet streams; however, small lakes are prevalent in glaciated landscapes but little is know about their influence on catchment hydrology. Important questions about lake-stream networks include: How do lakes influence downstream flow regimes and water quality? How far downstream do these lake effects persist? How does the lake-stream network structure impact streamflow and water quality at catchment scales? Are catchments with lakes more resilient to environmental change than catchments without lakes? The proposed research will address these questions using a combination of field and modelling approaches. Field research will be conducted at research catchments containing lake-stream networks in the rain-on-snow zone of the southern Coast Mountains in British Columbia. The field work will aim at characterizing the physical processes controlling the hydrology and thermal regimes of these catchments and their lake-stream networks. Both streamflow and water temperature are critical influences on fish growth, development, survival and distribution. The process knowledge gained from the field studies will be used to build and test computer models to improve our ability to predict effects of climate change and forest disturbance, and the role of lakes, on streamflow and water temperature. This model building and testing framework will drive rapid advances in catchment hydrology understanding, which will be critical for developing tools to effectively manage these systems.